1. Field of the invention
The present invention concerns packs for administration of sterile liquids including pharmaceutical, nutrient and energy-source liquids.
2. Description of the prior art
Each patient requires a different and extremely accurate dose of a different active product administered over an accurate time period in accordance with a personalized medical prescription that must be complied with absolutely.
In the current state-of-the-art this always requires as a preliminary stage the sterile transfer of a very accurate volume of sterile liquid from its industrial packaging to a delivery system which must be capable of administering asceptically and with extreme accuracy specified volumes of the sterile liquid.
This is particularly true in respect of cytostatic agents which are highly toxic and very aggressive. These products are therefore transferred in specialist hospital units employing special sterile rooms, sterile bubbles and laminar flow extractor cabinets in which the operative wearing breathing apparatus and gloves for protection measures out the required volume with extreme accuracy, transfers it into a special sterile transfer package and then places the latter in a sterile heat-sealed sachet which is then sent to the room of the patient concerned where the nurse, after opening the sachet, carries out a second transfer into the large capacity container of what is known as an injectable mass solute, the delivery system used most frequently in hospitals. These manual operations entail two transfers and require an additional and special transfer package, which makes them very costly, very difficult and very dangerous, not only to the preparation operative and to the nurses, because of the aggressive nature of these products, but also to the patients because the risks of contamination by microbes are increased by the number of transfers. Also, this first type of delivery system has many other disadvantages: very imprecise administration requiring constant and subjective surveillance by a nurse, with the attendant economic consequences, the impossibility of moving patients without a third person accompanying them and holding the large capacity container above them at all times, and the impossibility of administering such treatment at home.
In a second type of delivery system a motor moves the piston of a disposable syringe. This simplifies the transfer problem but because it requires a powerful motor and because the piston sticks easily, the delivery system is heavy, costly and sophisticated and incorporates safety systems (because of the risk of the motor racing), battery or AC line voltage power supply, all of which makes the treatment of ambulatory patients difficult and time-consuming.
A third type of delivery system is the infuser. Although this solves the weight problem it has many other disadvantages.
Filling requires an additional sterile transfer package in the form of a sterile syringe. When this has been filled, it must be used immediately because the dispensing of the sterile liquid begins. This rules out its advance preparation in specialist hospital units and industrial prepackaging, the latter being even less feasible given that the infuser is too costly because the entire system, comprising a pack with strongly elastic walls and an accurate flowrate regulator, is disposable. Because the system is not re-usable and because the liquid to be administered flows through it, apart from the economic repercussions, the volumes dispensed are not the same for liquids which have different viscosities, they cannot be varied for different patients to suit the medical prescription, and it is impossible to administer suspensions as these would clog the regulator. In some cases the elastomer constituting the walls of the pack, which is always the same, interacts with the product to be administered, in other words the product and the container may be incompatible.
Faced with the disadvantages summarized above, a general objective of the invention is to provide a pack for administering sterile liquids suitable for industrial prepackaging or for filling by aspiration direct from any other form of industrial packaging and then dispensing with extreme accuracy specified volumes of sterile liquids, and in particular dispensing these liquids with an extremely accurate preset flowrate determined by the medical prescription, which pack is capable of solving the problem of previous transfer into a delivery system, is capable of administering different volumes for different patients, offers a completely free choice of component materials to suit the product to be administered so that there is no interaction between them, is sufficiently light in weight and sufficiently reliable to be usable for treating ambulatory patients in total safety and with no requirement for any supply of electrical power, and enables a significant reduction in the weight and the cost of the apparatus with re-usable component parts.